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Page 189 Mach's Principle in its nineteenth-century form could be stated roughly as follows:
Mach's Principle (19th-Century Version): The distribution of matter everywhere in the universe determines the inertial frame at each point in the universe.
Page 191 Modified version of Mach's Principle: The distribution of matter and field energy-momentum everywhere at a particular moment in the universe determines the inertial frame at each point in the universe.
Page 193 Physicists have learned in the twentieth-century that electromagnetic fields and gravitational fields (as well as most others) carry energy and momentum, and concentrations of these fields can accurately mimic matter concentration. Indeed, electromagnetic fields can transform into elementary particle matter and vice versa; the same is true of gravitational fields. So knowledge of some parts of the electromagnetic and gravitational (and other) fields is needed, along with knowledge of matter fields directly, to determine inertia.
Page 216 Mach's 1873 passage: "Now what share has every mass in the determination of direction and velocity in the law of inertia?"
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